1. Field of the Invention
This invention relates generally to thermoformed, paperboard food containers, and more particularly to two part food containers which entirely enclose a prepared food product, maintain the quality of the food product and the appearance of both the food product and the container, while permitting the container to be reused multiple times for storing unconsumed portions of the food product.
2. Description of the Related Art
Many food containers, including those that hold pizza, are commonly made to be disposable after use for one food product. For example, pizza boxes are typically made from conventional, corrugated paperboard such as the pizza box illustrated in U.S. Pat. No. 4,441,626 to Hall, which discloses a pizza box formed from a double-sided corrugated blank. Other food containers, such as plates, bowls, clamshells and trays, are thermoformed or pressformed from relatively thin corrugated paperboard material such as the material described in U.S. Pat. No. 6,491,214 to Plummer, et al., which is herein incorporated by reference.
A pizza or other hot food product is placed inside the container or box and picked up by or delivered to the customer. The customer consumes some or all of the food and eventually disposes of the container in the trash. When less than all the food is consumed, the remaining food product is replaced in or remains in the container and is stored in the refrigerator.
Although these prior art container products have provided a substantial improvement over prior technology and have given good service to consumers, they continue to exhibit some deficiencies or undesirable characteristics.
Many of these containers have a fluid impervious layer or coating on one or more interior surfaces, most commonly a bottom, interior surface. This coating assists in maintaining the integrity of the container and resisting the transmission of fluids from the food products through the container material to present a distasteful, soiled external appearance to the container. However, the same coating on the bottom, interior surface also allows grease and other liquids, which are exuded from the food product, to pool on the impervious surface some of which soaks back into the food product. As a consequence, the food product becomes unpleasantly greasy and is seen by the consumer to be resting on an undesirably greasy surface.
If, instead, no liquid impervious layer is applied to the bottom surface, exuded grease, juices and moisture soak through the container bottom where they cause the container to exhibit a soiled appearance and can even stain an underlying tablecloth or other supporting surface. Some commercial establishments use an additional tray insert or soaker pad, which is typically a circular, corrugated disk placed on the interior bottom of the box to absorb or contain these exuded liquids. However, this adds further supply cost, consumes additional material and requires additional assembly time and labor.
Additionally, in the absence of a moisture impervious layer, the bottom can become soaked with liquids from the food product and become weakened and flimsy. The loss of sufficient rigidity makes the container, when held by the consumer, more likely to separate and tear or deform and allow the food product to spill out of the container.
When the container top is provided with a moisture impervious layer on its interior surface, moisture can condense from water vapor evaporated from the contained food product, collect into droplets instead of soaking into the container material and rain down onto the food product. This causes the top of the food product to become undesirably soggy in appearance and texture.
Conventional pizza boxes also require labor to assemble which adds to the cost and time for production of the final, deliverable product. Once assembled, they require considerable space for storage while awaiting the insertion of a pizza because they do not efficiently nest or stack in a vertical column. The conventional pizza box also relies on the friction fit of the lid or top against the sidewalls of the bottom and does not always close properly or remain tightly closed to keep the pizza fresh. Another problem is that the traditional square pizza box is bulky and often difficult to fit into a refrigerator. Because it has a round product in a square container, the square container uses approximately 8–10% excess, wasted material. Because of their size and bulk, they can be difficult to dispose of.
The problem of preventing a pizza from sitting on exuded grease and other liquids, while preventing unsightly penetration of those liquids through to the exterior surface of the container, was solved in U.S. Pat. No. 5,423,477 to Valdman et al. by coating the interior surface of the bottom with a liquid impervious layer but providing raised projections or ridges to hold the pizza above interposed valleys into which the liquids drained.
Another proposed solution to the same problem is described in U.S. Pat. No. 4,441,626 to Hall. There, two corrugated cardboards are laminated together with a moisture resistant glue. However, this requires the use of two corrugated layers and the step of gluing them together. Hall describes how this also requires the additional set up time and step for running the corrugating machine in a “backward” direction. Consequently, the Hall proposal involves significant additional material and manufacturing time and effort.
Applicant has been told that a food container was test marketed that was made from two, oppositely facing, conventional paper plates that were bonded together around their engaging rims. However, the products were not commercialized because of their serious deficiencies and inadequacies. The plates were made from paper rather than corrugated paperboard and therefore they lacked sufficient rigidity and thermal insulation characteristics. As a result, the container formed in this manner was too flimsy to hold the contained product and the rim was so flimsy that it warped and consequently did not permit the adhesive to be properly and evenly applied. Because of the inadequate insulation provided by paper, this container did not maintain the temperature of the enclosed food product for a sufficiently long time and also allowed its exterior surface to become hot to the touch, possibly resulting in a burning sensation or injury to the consumer. The paper material was unscored prior to forming the paper plates, which caused bunching of the paper material and formed wrinkles in the product. The wrinkles in the rim surfaces did not allow for the smooth application of the bonding material used to bond the plates together. The bonding material was not resealable and was intended only for a one-time use, like a shrink wrap. Additionally, this container was produced with a grease barrier coating on the upper surface of the lower plate, which the bonding material did not strongly adhere to and, therefore, released from major portions the rim when the container was pulled apart to access the contained product. This breaking of the bond with the paper plate in many, but not all, places allowed the plates to be physically separated but caused the bonding material which did remain bonded to form strings when the plates were separated. This stringing of the bonding material made the plates incapable of being resealed and the long strings of bonding agent could then fall onto the contained food product. In addition, the film barrier, placed on the inside of the lower plate, did not allow for the absorption of grease or water vapor and therefore, the grease or condensed liquid would “pool” on the surface and be reabsorbed by the contained food.
Therefore, it is an object and feature of the invention to provide a food container, particularly for pizza, which has top and bottom components which more efficiently use less material than conventional pizza boxes and are nestable so they can be stacked in compact columns, which does not require assembly, except for quick closure to enclose the pizza and which provides a stronger seal around its entire periphery.
Another object and feature of the invention is to provide a container having a bottom that not only allows the container bottom to soak up exuded liquids and maximizes liquid wicking and storage volume within the container, but also has a liquid barrier layer that prevents penetration of those liquids so that they do not cause an unsightly external container appearance.
Another object and feature of the invention is to provide top and bottom portions of the container that can be easily and strongly bonded together by a cohesive which is releasable and rebondable so the container can be reused for storing food products, that allows the top and bottom be used as two serving plates and that can be easily disposed of when no longer needed.
A further object and feature of the invention is to provide a container having a top that does not have a moisture barrier on its interior surface so the top can absorb moisture from the contained food product.
Another object and feature of the invention is to provide a food container, especially for pizza, which is made from thermoformed or pressformed corrugated material so that the container will be sufficiently rigid, can be manufactured at reduced cost, will provide thermal insulation, and will allow the top and bottom to be manufactured using the same die set.